5-methyl-dCTP deaminase induced by bacteriophage XP-12

Abstract

Bacteriophage XP-12, whose DNA contains 34 mol% 5-methylcytosine, induces the synthesis of a unique enzyme, 5-methyl-dCTP deaminase. The substrate for this enzyme, 5-methyl-dCTP, is produced by reactions catalyzed in part by other phage-induced enzymes, and the product of the reaction is dTTP. The deaminase therefore provides a novel pathway for biosynthesis of thymine residues for phage XP-12 DNA. Evidencd is presented that this pathway is used for dTTP synthesis in XP-12-infected Xanthomonas oryzae.

Biosynthesis and Function of Modified Bases in Bacteria and Their Viruses

“…In a manner analogous to the synthesis of dUMP from dCMP in the bacteriophage PBS1, dTTP in Xp12 infected cells is synthesized from m5 dCTP by a m5 dCTP-specific deaminase. 72 Together with the three canonical dNTPs, m5 dCTP is incorporated into DNA by a DNA polymerase, likely phage encoded. The in vitro resistance of m5 C-DNA to a wide range of restriction endonucleases suggests a protective role for m5 C in Xp12.…”

“…This diphosphate nucleotide is subsequently phosphorylated by a host-encoded NDK to yield m5 dCTP. In a manner analogous to the synthesis of dUMP from dCMP in the bacteriophage PBS1, dTTP in Xp12 infected cells is synthesized from m5 dCTP by a m5 dCTP-specific deaminase . Together with the three canonical dNTPs, m5 dCTP is incorporated into DNA by a DNA polymerase, likely phage encoded.…”